title: Increase in myopia prevalence in clinic-based populations across a century.
abstract: OBJECTIVE
  The study's aim was to report prevalence estimates and age-related trends in refractive error in a clinic-based series and compare them to results from studies of a similar nature conducted since 1892.
  
  
  METHODS
  Refractive error, patient age, and sex were collected from the files of all patients seen at the University of Waterloo School of Optometry and Vision Science clinic between January 2007 and January 2008. Patients were categorized as having myopia (<-0.5D mean ocular refraction [MOR]), hyperopia (>0.5D MOR), emmetropia, astigmatism (<-0.5D), and/or anisometropia (>1.0D difference between eyes). The prevalence of all refractive components was determined overall and in 1- and 5-year age groups, and then compared to data from older clinic-based studies. Refractive trends over time were noted. The prevalence of myopia and hyperopia were compared to older studies.
  
  
  RESULTS
  The lowest prevalence of myopia was 5% at 0 to 5 years of age, after which it increased to 72% at 20 to 30 years of age and then decreased to 22% in patients older than 70 years. A myopic peak occurred at 24 years of age. The prevalence of hyperopia followed opposite trends with a minimum prevalence of 6% at 25 to 30 years of age. Peaks in emmetropia prevalence were 55% at 5 to 10 years of age and 37% at 45 to 50 years of age. The prevalence of astigmatism and anisometropia increased with age. The Waterloo Eye Study showed a higher prevalence of myopia across all ages compared to the older studies with a peak prevalence of 72% compared to 21% in the oldest (Herrnheiser) study from 1892.
  
  
  CONCLUSIONS
  In the last 100 years, there appears to have been a myopic shift in clinic-based populations and myopia prevalence appears to follow a predictable pattern with age.
authors.affiliation: *OD, FAAO †OD, MSc ‡OD §OD, PhD School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Patricia K
authors.initials: PK
authors.lastname: Hrynchak
authors.forename: Andrea
authors.initials: A
authors.lastname: Mittelstaedt
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Machan
authors.forename: Carla
authors.initials: C
authors.lastname: Bunn
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Irving
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000453:epidemiology; D007223:Infant; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000453:epidemiology*; D009864:Ontario / Q000453:epidemiology; D015995:Prevalence; D012189:Retrospective Studies; D017678:Sex Distribution; D055815:Young Adult